Isolation and Identification of Cellulolytic Bacteria Involved in the Degradation of Natural Cellulosic Fibres

Abstract

In search for bacterial cultures that are able to rapidly degrade cellulosic plant fibres in vitro, 77 cellulolytic strains were isolated from Belgian and Czech soils after enrichment on flax or sisal fibres as sole sources of carbon. The strains were characterized using fatty acid analysis, and 74 strains were grouped into three major clusters by numerical analysis. The first major cluster contained Cellulomonas strains. Within this cluster three subclusters could be delineated by principal component analysis, that were recognized by their fatty acid compositions as Cellulomonas gelida, Cellulomonas biazotea and Cellulomonas cellulans, containing 9, 8 and 13 strains respectively. The second major cluster, with 9 strains, was assigned to Flavobacterium johnsoniae. The 34 strains of the third cluster could not be identified by commercial identification systems on the basis of their fatty acid profiles and API 20NE profiles. On the basis of their phenotypic characteristics they met the description of the genus Cellvibrio, their fatty acid profiles were similar to those of four authentic Cellvibrio mixtus strains, and the 16S rRNA genes from four representatives showed up to 97.8% sequence similarity to 16S rDNA from Cellvibrio mixtus ACM 2603. Three non-clustered strains were assigned to Curtobacterium flaccumfaciens, Achromobacter piechaudii and Pseudomonas mendocina. Two strains assigned to Cellvibrio were able to degrade several flax, broom and cotton fibres very rapidly in a standardized in vitro test, causing mass losses of 40 to 86% within 13 days of incubation, but not jute.